Many vertically operating doors have a pliable panel or curtain that opens by moving from a vertical set of tracks installed along the lateral edges of a doorway to an overhead storage system. The storage system can vary depending on the available space above the doorway and other considerations. An overhead storage system, for instance, can be in the form of a take-up roller that draws in the curtain to open the door; or the storage system can be a set of horizontal, vertical, or inclined tracks that lead into the set of vertical tracks that line the doorway.
While the take-up roller can be power-driven to raise and lower the curtain, doors having other types of overhead storage may require some other means for operating the door. Thus, door manufactures often need to offer a selection of doors of dramatically different designs to meet the requirements of various door installation sites.
U.S. Pat. No. 7,028,741, however, discloses a door with a drive system that can force-feed a curtain into various overhead configurations. Moreover, the door includes a breakaway feature that enables the curtain to safely break away from its guide track if a forklift or something else crashes into the door.
Although the force-feed system and breakaway feature provide significant benefits, the patented door includes a complicated collection of numerous parts. In some cases (FIG. 3 of the '741 patent), the curtain is coupled to a track via a drive strip that carries a long series of individual clips that enable the curtain to breakaway from the drive strip. In the event of an impact, the curtain can break away from those clips, while the drive strip remains with the track. It appears that a complicated mechanism (FIG. 19 of the '741 patent) is subsequently used for reattaching the curtain to the clips.
In other cases (FIG. 5 of the '741 patent), the numerous clips are replaced by a drive strip that is blanked and formed to include integral clips. But even then the drive strip remains with the track after a breakaway collision, thus the door has a curtain that can move relative to a drive strip, which in turn can move relative to a track. Moreover, it appears that the drive strip with the integral clips is made of sheet metal. Such a material, particularly if it has sharp edges, might cause significant wear on the gear that moves the drive strip.
Consequently, a need exists for a vertically operating door that is simple and robust, wherein the door includes a drive unit that can push the door's curtain to various overhead storage configurations including vertical, horizontal, inclined and coiled.